66 FIRST FORMS OF VEGETATION. 
a close resemblance to the glandular structure of 
the stems of coniferous trees. The seed-vessel 
rises among the leaves on a peduncle resembling a 
fruit-stalk, and bursts in the centre, the lid flying 
off when the seed is ripe with considerable force. 
It is extensively distributed in temperate regions, 
being almost unknown in the tropics, where the 
peat is formed by the decomposition of shrubby 
plants like the common heather. The peat of 
Tierra. del Fuego, the Falkland Islands, and the 
Galapagos Archipelago, is composed of this bog- 
moss. It is geographically interesting to find a 
species, Sphagnum <Austini, not rare in North 
America, growing on boggy moors and forming 
large hummocks sometimes two feet above the 
surrounding level, in the Island of Lewis, one of 
the Hebrides, the only place in which it has yet 
been found in this country. We may be able to 
form some idea of the vast importance of the 
Sphagna, when we consider that peat-bogs occupy 
a tenth part of the whole of Ireland, and furnish in 
the Highlands of Scotland the largest proportion 
of the fuel consumed by the inhabitants. It is a 
singular fact that we owe our coals to the carbon- 
ized remains of ferns and their allies; and our 
peats to the decomposed tissues of mosses—two of 
the most useful and indispensable materials in our 
social economy to two of the humblest families in 
